WP4 – Map-making Module



Integrate the Madam map-making code into the pipeline.

Description of work

Map-making in a standard CMB analysis chain compresses the time-ordered data into sky maps. The pre-processed data, however, contains contributions from instrumental noise, which if left untreated will alter the statistical properties of the resulting maps. For the Planck LFI radiometers the noise model consists of two independent components: white (uncorrelated) and 1/f (correlated) noise (J. Delabrouille, A&A Supp. Serr. 127:555-567, 1998). The untreated 1/f noise component shows up in the resulting maps as stripy features. Hence, in addition to visualising and compressing data, a proper map-making algorithm aims to remove the 1/f noise, while processing the CMB and astrophysical signals and white noise as little as possible.

Map-making step in the BeyondPlanck work is performed with the Madam map-maker code (E. Keihanen et al, A&A, 510:A57, 2010). The code is fully functional, and it has been the main map-making tool of the LFI DPC. Madam map-maker is based on a destriping principle (C. Burrigana et al., astro-ph/9906360, 1999), where the 1/f noise component is modelled by a sequence of constant offsets, called baselines. Further, the Madam map-maker is able to use a noise prior to constrain baseline amplitudes (E. Keihanen et al., A&A, 510, A57, 2010), which allows us to shorten the baseline length considerably.

Our aim is to integrate the Madam map-maker with the BeyondPlanck pipeline in such a way that it can be run repeatedly as part of the automatized pipeline. Additionally the work pakgage 4 consists of testing and validating the map-making module.